Angular speed=linear speed/radius. One revolution = 2π radian = 6.2832 radians approx.
One revolution per hour would be 2π=6.2832 radians per hour, 15 revs/hr=30π rads/hr=π/2 rads/minute.
Linear speed of car on the ferris wheel would be 26×angular speed=13π ft/minute=40.84 ft/min or 0.68 ft/sec approx.